Copper alloy for use at high temperatures

ABSTRACT

THE ALLOY OF COPPER BASE GENERALLY COMPRISES ZINC, NICKEL AND A SMALL AMOUNT OF TITANIUM AND CHROMIUM WITH ADDITION OF A SMALL AMOUNT OF SILICON AND LEAD WHEN DESIRED. WITH THESE CONSTITUENT ELEMENTS, AN ALLOY OF IMPROVED MECHANICAL STRENGTH AND CORROSION RESISTIVITY AT HIGH TEMPERATURES IN THE RANGE OF FROM 300 TO 400*C. IS OBTAINED.

United States Patent US. Cl. 75--134 2 Claims ABSTRACT OF THE DISCLOSURE tained.

The present invention relates to a novel alloy of copper base whose mechanical strength and corrosion resistivity at high temperatures have remarkably been improved as compared with conventional copper alloys and which is suitable as a material for valve bodies in valves to be used at high temperatures and under high pressures.

In industries of recent years, there is a general tendency in the fluid conditions that the level of pressure required becomes ever higher with gradual increase in temperature. The valves to be used under such severe conditions should, therefore, be capable of performing excellent closing function and in addition, the valve bodies themselves must be provided with highly improved strength. However, a conventional copper alloy such as bronze or brass which is extensively used as a material for valve bodies has, in general, lower mechanical strength than other steel materials, and at high temperatures exceeding 250 C., it has been considered to be dangerous to use such an alloy. Furthermore, the acid-resisting property to copper alloy, though substantially superior to that of common steel materials, is by no means perfect.

A principal object of the present invention is to provide a novel copper alloy which has extremely high mechanical strength at temperatures in the range of from 300 to 400 C.

Another object of the present invention is to provide a copper alloy which has resistance to corrosion caused by acids and chemicals and which is capable of resisting erasion produced by fluids of high temperature and high pressure.

Still another object of the present invention is to provide a copper alloy which is suitable for casting and forging and well adapted for machining such as cutting.

The principle of the present invention, generally stated, consists in that zinc, nickel, a very small amount of titanium and chromium are added to copper base to improve the mechanical properties of conventional copper alloys, 2. small amount of silicon and/ or lead further being added thereto when desired. That is to say, the copper alloy of ice the present invention contains following constituent elements:

Zinc3 8-43 Nickel-5-l5 Chromium-0.1-1.0% Titanium-0.3 or less Silicon0% or not more than 0.5% Lead-0% or not more than 0.5% CopperBalance In this alloy, with the presence of not more than 0.3% of titanium content, the crystalline particles of metal are made extremely fine with the result that the strength and corrosion resistance have remarkably been improved. The nickel and chromium contents in the above-mentioned range also greatly contribute to the increase of the mechanical strength of the alloy. Moreover, silicon is advantageous in providing the allow an ability to retain its mechanical strength which tends to be markedly impaired around a temperature of 350 C. The addition of lead also proves effective in improving machinability. The most desirable amount of titanium to be contained in the alloy of the present invention is 0.02 to 0.2% and that of chromium is in the range of 0.3 to 0.7%, while in case silicon is to be added, a favorable silicon content is in the range of 0.05 to 0.1%.

Although an outstanding effect can be achieved by adding an extremely slight amount of titanium, no improved eflect is observed when 0.3% or more of titanium is present in the alloy, hence it is unnecessary to increase the amount of titanium. It is found out that the chromium content, when exceeding 1.0%, results in increase in hardness, which is liable to be detrimental to the machinability and the properties in the high temperature range.

The nickel content in the alloy of the invention may most preferably be in the range of 8 to 13%, and when it is reduced to 5% or less, the strength, particularly tensile strength may be greatly impaired, while even in case it is increased to more than 15 substantial improvement can not be obtained, so that for reasons such as economical, the upper limit is set at 15% Most preferably, the zinc content in the alloy of the invention is 40 to 42%, and when it is reduced to 37% or less, or when it is increased to 44% or more, the characteristics of the alloy will be subjected to objectionable influence.

Although the alloy of the present invention does not necessarily require the addition of silicon and lead, a small amount of silicon, when added thereto as set forth above, can apparently render the properties of the alloy at high temperatures stable. In case the silicon content exceeds 0.5%, however, the mechanical strength at a normal temperature becomes deteriorated. An attempt to add a small amount of lead to the alloy remarkably enhances the ease of cutting work. Such constituents may be added to the alloy as desired in accordance with the use of the alloy and the purpose for which it is used.

Table 1 below presents compositions of some examples of the alloys in accordance with the foregoing ranges of the present invention as they are compared with the are left therein for an hour. The reduced amount per unit surface area of the samples are thereafter measured. It is evident that the alloy has corrosion resistivity to acid by far superior to those of other metals.

What is claimed is:

1. A copper alloy adapted for use at a high temperature consisting of the following constituents in the folcompositions of bronze and brass which are conventionally used in general.

TABLE 1 Percent 011 Zn Ni Ti Cr Aliloys otf the nven ion No.1 Balance 42.0 10.0 o 2 0.2 lowmg Proportlon' 4 .0 10. 0 0 2 0. Percent 0 10.0 0 2 0 Zi 42 Nickel Chromium 0.2 Table 2 shows compartive values of mechanical strength Titanium 0.2 of sample castings given in the above table, as it is meas- S1l1con 0.2 ured at each of the given temperatures. Copper Balance TABLE 2 Normal temperature 235 0. 300 0. 350 0. 400 C.

Tensile Elon- Tensile Elon- Tensile Elon- Tensile Elon- Tensile Elon- Hardness strength, gation, strength, gation, strength, gatlon, strength, gation, strength, gation (Hv) kgJmm. percent kg./mm. percent kgJmm percent kgJmrn. percent kgJmrn. percent 148 59.0 33.4 48 0 24. 0 37 6 l2. 8 33.1 10.0 29.8 8 0 164 57. 7 20. 0 52 5 22. 2 42. 8 17. 0 40. 9 17. 0 35. 0 l5 8 146 57. 1 23. 0 38- 0 12. 0 35. 0 8 0 68 24. 5 29. 8 15. 5 11. 2 8. 2 5- 5 6.0 4. 0 62 22. 8 37. 5 12. 2 l5. 0 7 5 8. 0 5- 2 5. 5

2. A copper alloy adapted for use at a high temperature consisting of the following constituents in the following proportion:

From the overall results of the tests set forth above, it will be apparent that the alloys of the present invention containing a small amount of titanium and chromium have remarkably improved mechanical properties Percent as compared conventional copper alloys without these Zinc 42 chemical constituents. Nickel 10 The acid-resisting property of the alloy in accordance Chromium 0.2 with the invention is shown in following Table 3 in com- Titanium 0,2 parison with those of principle metals. S ic0n 0.2 Lead 0.1

TABLE 3 References Cited Anzou it f 0r 5 i 5 UNITED STATES PATENTS va ueso re uce 1 338 518 4/1920 Mllllken 75--157 5 Samples: amount in mg./mm.

Alloy of the invention (No. 1 0.0074 337L026 3/1968 chnstme Bronze-6 (LLS. BC6) 0.0192 FOREIGN PATENTS i k ii m 3%;; 19,757 8/1968 Japan 75-1575 ron as 1 OTHER REFERENCES The method for measuring the amount of corrosion set forth above is as follows: For 20 hours and at a room temperature, each of the samples having a given surface area is immersed in a solution containing 10% of hydrochloric acid which serves as a corrosion-producing liquid. The solution is then heated to C. and the samples Copper, Butts, Reinhold Pub. Corp., N.Y., 1954, pp. 626-628.

50 CHARLES N. LOVELL, Primary Examiner US. Cl. X.R. 

